You can use DBCA in silent mode to delete a database instance from a node.
Run the following command, where the variables are the same as those shown in Table 10-1 for the DBCA command to add an instance. Provide a node name only if you are deleting an instance from a node other than the one on where DBCA is running as shown in the following example where password is the password:
dbca -silent -deleteInstance [-nodeList node_name] -gdbName gdb_name -instanceName instance_name [-sysDBAUserName sysdba -sysDBAPassword password]
At this point, you have accomplished the following:
Deregistered the selected instance from its associated Oracle Net Services listeners
Deleted the selected database instance from the instance's configured node
Removed the Oracle Net configuration
Deleted the Oracle Flexible Architecture directory structure from the instance's configured node.